Anticancer efficacy of Magainin2 and analogue peptides.

Linear helical channel-forming peptides structurally similar to the Xenopus-derived antibiotic, Magainin2-amide, were synthesized. Because activity resides in the physicochemical properties of the peptides, an all-D-amino acid as well as an all-L-amino acid sequence were tested for anticancer activity. In vitro activity against carcinoma cells and in vivo efficacy against four murine ascites tumors were determined. The novel peptides proved to have enhanced potency in vitro and in vivo as compared to the parent compound. The 50% inhibitory concentrations against A549 cells for the all-D, the all-L, and Magainin2 were 6, 10, and 110 micrograms/ml, respectively. All three peptides had activity against P388 leukemia, S180 ascites, and a spontaneous ovarian tumor when injected i.p. Increase in life span of over 100% was produced for the analogues in the latter two models. The maximally effective concentrations for the analogues were 20 to 25 mg/kg while Magainin2 required 50-60 mg/kg for in vivo efficacy. The all-D-amino acid peptide, MSI-238, proved as effective as doxorubicin at a more advanced stage of the ovarian tumor and this activity may be attributed to its resistance to proteolytic degradation. Therefore, this class of amphiphilic alpha-helical cationic peptides has potential in the peritoneal treatment of ovarian cancer.